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1.
Inorg Chem ; 59(15): 10673-10687, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32666791

RESUMO

A series of isostructural homo- and heterolanthanide coordination polymers of formula [Ln2(dcpa)3(H2O)]∞ with Ln = La-Gd have been obtained by reactions in water between the lightest lanthanide chlorides and the disodium salt of 4,5-dichlorophthalic acid (H2dcpa). They present particularly high thermal stability for coordination compounds (up to 400 °C). Their luminescent properties have been studied in detail. Interestingly an insensitivity to water coordination as well as a very strong effect of optical dilution is observed. Therefore, molecular alloys with very high lanthanum concentration have been prepared. Some of them present highly tunable and very intense luminescence. For example, to the best of our knowledge, [Sm0.04La1.96(dcpa)3(H2O)]∞ presents one of the highest overall quantum yields measured so far for a Sm3+-based coordination compound (QSmLigand = 9.2%), and [Nd0.03Sm0.14Eu0.03La1.8(dcpa)3(H2O)]∞ is one of the brightest (12 Cd·m-2 under 0.75 mW·cm-2 UV flux) multiemissive visible and near-infrared lanthanide-coordination polymers reported to date.

2.
Inorg Chem ; 59(15): 11028-11040, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32667813

RESUMO

Reactions in water of lanthanide chlorides with the sodium salt of 4,5-dichlorophthalate (dcpa2-) lead to two families of isostructural coordination polymers: family F1 that gathers compounds with the general chemical formula [Ln2(dcpa)3(H2O)]∞ with Ln = La-Gd (except Pm) and family F2 that gathers compounds with general chemical formula [Ln2(dcpa)3(H2O)5·3H2O]∞ with Ln = Tb-Lu plus Y. Heterolanthanide molecular alloys that contain both Eu3+ and Tb3+ ions have been prepared in both structural families. Their luminescence properties have been studied, especially from the brightness point of view. This study revealed that structural family F1 provides molecular alloys that are much more luminescent than those of structural family F2. Therefore, a phase-induction strategy was followed that allowed the design of some molecular alloys (La/Tb/Eu and La/Dy) that are, to the best of our knowledge, among the most luminescent coordination polymers reported so far. This study opens the way to bright luminescent bar codes as well as to bright white luminescent lanthanide-based coordination polymers.

3.
Inorg Chem ; 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32521161

RESUMO

The size, morphology, and purity control of coordination compound powders is a key stage for their conversion into materials and devices. In particular, surface science techniques require highly pure bulk materials with a narrow crystallite-size distribution together with straightforward, scalable, and reproducible crystallization procedures. In this work we demonstrate how sonocrystallization, i.e. the application of ultrasound during the crystallization process, can afford very quickly powders made of crystallites with controlled size, morphology, and purity. We show that this process drastically diminishes the crystallite-size distribution (low polydispersity indexes, PDI) and crystallite aspect ratio. By comparing sonicated samples with samples obtained by various silent crystallization conditions, we unambiguously show that the improvement in the crystallite morphology and size distribution is not due to any thermal effect but to the sonication of the crystallizing media. The application of sonocrystallization on crystallization batches of single-chain magnets (SCMs) maintains the chemical integrity of the SCMs together with their original magnetic behavior. Moreover, luminescent measurements show that sonocrystallization induces an efficient micromixing that drastically enhances the purity of the SCM powders. We thus propose that sonocrystallization, which is already used on organic or MOF compounds, can be applied to (magnetic) coordination compounds to readily afford bulk powders for characterization or shaping techniques that require pure, morphology- and crystallite-size-controlled powder samples.

4.
Angew Chem Int Ed Engl ; 59(2): 780-784, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31682058

RESUMO

We report a single-chain magnet (SCM) made of a terbium(III) building block and a nitronyl-nitroxide radical (NIT) functionalized with an aliphatic chain. This substitution is targeted to induce a long-range distortion of the polymeric chain and accordingly it gives rise to chains that are curled with almost 20 nm helical pitch. They self-organize as a chiral tubular superstructure made of 11 chains wound around each other. The supramolecular tubes have a 4.5 nm internal diameter. Overall, this forms a porous chiral network with almost 44 % porosity. Ab initio calculations highlight that each TbIII ion possesses high magnetic anisotropy. Indeed, notwithstanding the supramolecular arrangement each chain behaves as a SCM. Magnetic relaxation with both finite and infinite-size regimes is observed and confirms the validity of the Ising approximation. This is associated with quite strong coercive field and magnetic remanence (Hc =2400 Oe MR =2.09 µB at 0.5 K) for this class of compounds.

5.
J Am Chem Soc ; 142(2): 931-936, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31880442

RESUMO

A one-dimensional coordination solid 1c is synthesized by reaction of a bispyridyl dithienylethene (DTE) photochromic unit with the highly anisotropic dysprosium-based single-molecule magnet [Dy(Tppy)F(pyridine)2]PF6. Slow magnetic relaxation characteristics are retained in the chain compound 1c, and photoisomerization of the bridging DTE ligand induces a single-crystal-to-single-crystal transformation that can be monitored using photocrystallography. Notably, the resulting chain compound 1o exhibits faster low-temperature relaxation than that of 1c, which is apparent in magnetic hysteresis data collected for both compounds as high as 4 K. Ab initio calculations suggest that this photomodulation of the magnetic relaxation behavior is due to crystal packing changes rather than changes to the crystal field splitting upon ligand isomerization.

6.
Inorg Chem ; 58(23): 16180-16193, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31714756

RESUMO

Reactions in solvothermal or microwave-assisted conditions between a hexanuclear rare-earth entity ([Ln6] with Ln = Eu-Dy) and m-halogeno-benzoic acids lead to three series of isostructural complexes with respective chemical formulas [Ln6(µ3-OH)2(H2O)2(NO3)2(3-cb)14]·4CH3CN, [Ln6(µ3-OH)2(H2O)2(NO3)2(3-bb)14]·6CH3CN, and [Ln6(µ3-OH)2(H2O)2(NO3)2(3-ib)14]·6CH3CN, where 3-cb-, 3-bb-, and 3-ib- represent 3-chloro-, 3-bromo-, and 3-iodo-benzoate, respectively. These three series of compounds are almost isostructural. Their luminescent properties, in the solid and solution states, have been studied in detail and compared. This study shows that hexanuclear complexes own strong intermetallic energy transfers. This makes these complexes good candidates for thermometric probes in solid state or in solution state.

7.
Dalton Trans ; 48(42): 16053-16061, 2019 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-31612893

RESUMO

We report the synthesis, ab initio calculations, magnetic and optical characterization of a DyIII-based dimeric compound named DyAZO. The dimers self-organize into a supramolecular chain decorated with photo-isomerizable azobenzene ligands. DyAZO displays single-molecule magnet (SMM) behavior. However, ab initio calculations highlight a quite strong admixture of MJ states of the 6H15/2 level of DyIII ions, the presence of low-lying excited MJ states and antiferromagnetic Dy-Dy dipolar coupling. This favors zero-field fast tunneling. Accordingly the Dy-doped analogue YDyAZO (5.5% Dy doping) displays enhanced magnetic relaxation with a hysteresis that is observed at 0.5 K. The influence of the cis- to trans-isomerization of the decorating azobenzene ligand on magnetic properties has been tested for both solid samples and solutions of DyAZO and YDyAZO. This provides hints for the synthesis of future Dy-based photo-isomerizable molecules.

8.
Inorg Chem ; 58(4): 2659-2668, 2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30730721

RESUMO

Isostructural lanthanide-based coordination polymers that are obtained by reactions in water of a lanthanide chloride and the sodium salt of 5-methoxyisophthalate (mip2-) have the general chemical formula [Ln2(mip)3(H2O)8·4H2O]∞ with Ln = Nd-Er except Pm plus Y (symbolized by [Ln2(mip)3]∞). Some of these homo-lanthanide compounds present very high luminescence brightness. The weak intermetallic energy transfer between lanthanide ions observed in these compounds allows the design of hetero-lanthanide coordination polymers with tunable luminescence properties. A molecular alloy that involved six different lanthanide ions (Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+) has been prepared and its luminescent properties have been studied. This compound, under a unique irradiation wavelength (λexc = 325 nm), exhibits almost 20 emission peaks in both the visible and the NIR regions at room temperature. This unprecedented richness of the emission spectrum could be of great interest as far as luminescent bar-codes are targeted.

9.
Inorg Chem ; 58(2): 1317-1329, 2019 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-30596502

RESUMO

Microcrystalline core-shell powders of lanthanide-based coordination polymers with general chemical formula ([Ln(cpbOH)]∞)1- x@([Ln'(cpbOH)]∞) x with Hcpb = 1,4-carboxyphenylboronic acid have been synthesized and structurally characterized. Their luminescent properties have been studied. They are drastically different from those of heterolanthanide coordination polymers, also called "molecular alloys", that present the same crystal structure and chemical composition. Study of the photophysical properties of core-shell lanthanide-based coordination polymers reveals that it is possible to control efficiently the intermetallic energy transfers between lanthanide ions. Furthermore, multiemissive compounds, under unique irradiation, in both visible and infrared regions are easily feasible. Core-shell microstructured lanthanide-based coordination polymers have also been prepared with terephthalic (H2bdc) and trimesic (H3tma) acids as ligands for evidencing that lanthanide-ion-based coordination compounds are excellent candidates for 3D molecular epitaxial growth.

10.
Inorg Chem ; 58(1): 462-475, 2019 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-30540189

RESUMO

Reactions in water of lanthanide chlorides with the sodium salt of 1,4-carboxyphenylboronic acid lead to two series of isostructural compounds with respective general chemical formulas [Ln(cpb)3(H2O)2]∞ for Ln = La or Ce and [Ln(cpbOH)(H2O)2·(cpb)]∞ for Ln = Pr-Lu (except Pm) plus Y. Heterolanthanide coordination polymers that are isostructural to the second series have been synthesized, and their photophysical properties have been studied. This study evidences that it is possible to design multiemissive lanthanide-based coordination polymers that could find their application as multigauge luminescent thermometric probes.

11.
Inorg Chem ; 57(17): 11044-11057, 2018 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-30130101

RESUMO

The rational design of molecular chains made of 4f ions and substituted 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical is presented. The reaction of Ln(hfac)3·2H2O (hfac- = hexafluoroacetylacetonate) and the 4-cyano-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-CN) radical affords air- and moisture-stable isostructural molecular chains of the formula [Ln(hfac)3TEMPO-CN] n for Ln = GdIII and TbIII, whereas zero-dimensional complexes of the formula [Dy(hfac)3(TEMPO-CN)2][Dy(hfac)3(H2O)2]2 are obtained for Ln = DyIII. To the best of our knowledge, the Gd derivative, Gd-TEMPO-CN, shows one of the strongest antiferromagnetic (AF) couplings for Gd-radical pairs ever reported with JGd-rad/ kB = -21.18 K, 14.72 cm-1 ( H = - JSrad SGd spin Hamiltonian convention). The TbIII derivative, Tb-TEMPO-CN, also shows strong Tb-radical AF coupling, which has been rationalized using the ab initio CASSCF approach ( JTb-rad = -23.02 K, -16.7 cm-1) and confirmed by luminescence measurements. Tb-TEMPO-CN shows remarkable properties for a Tb-radical-based single-molecule magnet ( Ueff = 69.3 ± 1 K; τ0 = 1.3 × 10-7 s) and two different relaxation processes triggered by interchain magnetic coupling.

12.
Chem Commun (Camb) ; 54(56): 7826-7829, 2018 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-29947367

RESUMO

Muon spin relaxation (µSR) experiments on a single-molecule magnet enriched in different Dy isotopes detect unambiguously the slowing down of the zero field spin dynamics for the non-magnetic isotope. This occurs in the low temperature regime dominated by quantum tunnelling, in agreement with previous ac susceptibility investigations. In contrast to the latter, however, µSR is sensitive to all fluctuation modes affecting the lifetime of the spin levels.

13.
Dalton Trans ; 47(13): 4722-4732, 2018 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-29537422

RESUMO

Single crystal diffraction studies reveal the formation of the following 10 new complexes of lighter Ln(iii) ions with general formulas {[Ln(µ2-L1)3·(H2O)2]·H2O}n (Ln = Nd (1) and Eu (2)), [Nd(µ2-L2)2·(CH3COO)·(H2O)2]n (3), [Ln2(µ2-L2)5·(L2)·(H2O)4]n (Ln = Sm (4), Ce (5), and Pr (6)), [La2(µ2-L2)6·(H2O)3·(DMF)]n (7) (DMF = dimethylformamide), [Ln(µ2-L2)2·(L2)·(H2O)3]2 (Ln = Eu (8) and Gd (9)) and [Gd(L2)·(CH3COO)2·(H2O)2]2 (10), where L1 and L2 are anions of 3,5- and 2,4-dinitrobenzoic acid, respectively. Complexes 1-7 are 1D coordination polymers, while 8-10 are dinuclear complexes. The luminescence properties of Nd(iii) and Eu(iii) analogues displayed metal-centred emission with L1 exhibiting weak but more efficient sensitization than L2. A study of the magnetic properties of the compounds clearly demonstrated the field-induced single ion magnet behaviour of the Nd(iii) compounds 1 and 3. Their behaviour has been compared to previously reported analogous Nd(iii) complexes and the role of the lattice solvent and polymorphism on the magnetic behaviour has been evaluated.

14.
Chemistry ; 24(27): 6983-6991, 2018 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-29436739

RESUMO

We report the study of a Dy-based metal-organic framework (MOF) with unprecedented magnetic properties. The compound is made of nine-coordinated DyIII magnetic building blocks (MBBs) with poor intrinsic single-molecule magnet behavior. However, the MOF architecture constrains the MBBs in a one-dimensional structure that induces a ferromagnetic coupling between them. Overall, the material shows a magnetic slow relaxation in absence of external static field and a hysteretic behavior at 0.5 K. Low-temperature magnetic studies, diamagnetic doping, and ab initio calculations highlight the crucial role played by the Dy-Dy ferromagnetic interaction. Overall, we report an original magnetic object at the frontier between single-chain magnets and single-molecule magnets that host intrachain couplings that cancel quantum tunneling between the MBBs. This compound is evidence that a bottom-up approach through MOF design can induce spontaneous organization of MBBs able to produce remarkable molecular magnetic materials.

15.
Inorg Chem ; 57(6): 3399-3410, 2018 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-29481066

RESUMO

Reactions in water of 4,5-dichlorophthalate (dcpa2-) with the heaviest lanthanide ions lead to a family of compounds with the general chemical formula [Ln2(dcpa)3(H2O)5·3H2O]∞, where Ln = Tb-Lu, Y. The synthesis, crystal structure, thermal behavior, and luminescent properties of this series of homonuclear compounds are described. Additionally, this family can be extended to isostructural heteronuclear compounds that can contain some light lanthanide ions and therefore present some original photophysical properties. These compounds show potential interest as multiemissive materials (visible and infrared light between 450 and 1600 nm) and could find application as luminescent bar codes.

16.
Dalton Trans ; 47(12): 4139-4148, 2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29469160

RESUMO

We report the synthesis of two lanthanide complexes including a chelating merocyanine (MC) ligand obtained from the reaction of a bis(pyridinemethyl)amine substituted spiropyran with yttrium(iii) or dysprosium(iii) triflate salts, whose structures were confirmed both in the solid state and in solution by single crystal X-ray diffraction studies and NMR investigations. The obtained merocyanine metal complexes can reversibly undergo a photo-triggered transformation consisting of a partial isomerization of the trans-merocyanine ligand to its cis isomer (cis-MC) providing complexes in which the metal-phenolate bond is retained. SQUID magnetometry experiments in combination with ab initio calculations were used to evidence and rationalize the single-molecule magnet behavior of the dysprosium complex and to probe the changes in the dysprosium ion local environment upon photo-isomerization.

17.
Inorg Chem ; 56(23): 14632-14642, 2017 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-29125752

RESUMO

Reaction of hexanuclear octahedral molecular precursors with a 3-chlorobenzoate ligand affords an unprecedented family of isostructural polylanthanide complexes via solvothermal and microwave-assisted syntheses in an acetonitrile medium. The general chemical formula of the compounds that constitute this series is {[Ln6(µ3-OH)2(H2O)2(NO3)2(3-cb)14]·(CH3CN)4}, where 3-cb- stands for 3-chlorobenzoate and Ln = Eu, Tb, Dy, Ho, Er, or Y. The crystal structure, solubility, and magnetic and luminescent properties of these complexes have been studied. The luminescent properties evidence that the composition of the hexalanthanide precursor is preserved during the synthetic process that is of particular interest for cases in which heterolanthanide complexes are targeted.

18.
Inorg Chem ; 56(12): 6788-6801, 2017 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-28558238

RESUMO

We report a combined theoretical and experimental investigation of the exchange interactions governing the magnetic behavior of a series of nitronyl nitroxide (NIT)-based Y(III) complexes, i.e., Y(hfac)3(NIT-R)2 with R = PhOPh (1), PhOEt (2), and PhOMe (3a, 3b). Even though some of these complexes or their Dy(III) parents were previously described in the literature [ Zhao et al. Transition Met. Chem. 2006 , 31 , 593 ; Bernot et al. J. Am. Chem. Soc. 2009 , 131 , 5573 ], their synthesis procedure as well as their structural and magnetic properties were completely reconsidered. Depending on the nature of R and the crystallization conditions, Y(hfac)3(NIT-R)2 units can be organized as supramolecular dimers or linear or orthogonal chains. Such structural diversity within the series induces extremely different magnetic behaviors. The observed behaviors are rationalized by state-of-the-art wave function-based quantum-chemical approaches (CASSCF/DDCI) that demonstrate the existence of not only effective intramolecular interactions between the NIT-R radical ligands of an isolated Y(hfac)3(NIT-R)2 molecule but also intermolecular interactions between NIT-R moieties belonging to different Y(hfac)3(NIT-R)2 units. These results are supported by the use of spin Hamiltonian models going beyond the basic Bleaney-Bowers formalism to properly fit the experimental magnetic data. Finally, the microscopic mechanisms behind the evidenced intramolecular exchange interactions are elucidated through the inspection of the calculated wave functions. In particular, whereas the role of Y orbitals was already proposed, we herein demonstrate the contribution of the hfac- ancillary ligands in mediating the magnetic interactions between the NIT radicals.

19.
Chemistry ; 22(43): 15222-15226, 2016 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-27595499

RESUMO

A spiropyran-based switchable ligand isomerizes upon reaction with lanthanide(III) precursors to generate complexes with an unusual N3 O5 coordination sphere. The air-stable dysprosium(III) complex shows a hysteresis loop at 2 K and a very strong axial magnetic anisotropy generated by the merocyanine phenolate donor.

20.
ACS Appl Mater Interfaces ; 8(24): 15551-6, 2016 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-27244645

RESUMO

Switching luminescence of lanthanide-based molecules through an external electric field is considered as a promising approach toward novel functional molecule-based devices. Classic routes use casted films and liquid electrolyte as media for redox reactions. Such protocol, even if efficient, is relatively hard to turn into an effective solid-state device. In this work, we explicitly synthesize lanthanide-based dimers whose luminescent behavior is affected by the presence of Cu(2+) ions. Excellent evaporability of the dimers and utilization of Cu(2+)-based solid-state electrolyte makes it possible to reproduce solution behavior at the solid state. Reversible modulation of Cu(2+) ions transport can be achieved by an electric field in a solid-state device, where lanthanide-related luminescence is driven by an electric field. These findings provide a proof-of-concept alternative approach for electrically driven modulation of solid-state luminescence and show promising potential for information storage media in the future.

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